**6. Angiogenesis in carotid atherosclerotic lesions**

Normal human intima is devoid of blood vessels, [52] however newly formed blood vessels are often seen within atherosclerotic plaques [53-56] (figure-3). The presence and density of these new blood vessels in carotid atherosclerotic lesions has been associated with the histological features of plaque instability and intra-plaque haemorrhage as well as the


**Table 2.** Features of Rupture prone (Unstable) Plaques [40]

development and timing of ipsilateral ischaemic or ocular events and presence of ipsilateral cerebral infarction on computer tomography (CT) scanning. [57-62] Microarray gene chip analysis revealed that the presence of newly formed vessels is associated with increased angiogenic gene expression. [63, 64] These new blood vessels are weak and could be respon‐ sible for intraplaque haemorrhage. Moreover, the endothelial lining of these microvessels express high levels of E-Selectin, ICAM-1, and VCAM-1, which indicates that these endothelial cells are in an activated state. Activated endothelial cells act as local site of inflammatory cell recruitment into the atherosclerotic plaque, perpetuating the inflammatory process within the lesion and contribute to plaque destabilization. [65-69]

There is ample clinical and histological evidence that carotid atherosclerotic plaques with large necrotic lipid core, thin plaque cap or ulceration, dense inflammatory infiltrate, intra-plaque haemorrhage and angiogenesis are vulnerable to rupture and development of ischaemic neurological and ocular events. In vivo identification of these changes within carotid athero‐ sclerotic plaques gives these findings clinical significance in the context of patients with significant carotid atherosclerosis. For over two decades, non-invasive imaging modalities such as duplex ultrasound and magnetic resonance imaging have been in clinical use. They have been used for the measurement of internal carotid artery stenosis. [79-81] These imaging modalities can also be used to study morphological changes associated with plaque instability

Carotid Plaque Morphology: Plaque Instability and Correlation with Development of Ischaemic Neurological Events

http://dx.doi.org/10.5772/57254

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**Figure 3.** New blood vessels in a carotid atherosclerotic plaque. (*Ann Vasc Surg* 2008; 22(2): 266–272.)

and development of ischaemic neurological events. [82-85]

**8. Duplex ultrasound assessment of carotid plaque morphology**

Duplex ultrasound is arguably the most important imaging modality for preoperative assessment of patients with carotid atherosclerotic disease. It is non-invasive, relatively inexpensive and very accurate at identification of significant ICA stenosis. [87-92] In measuring the degree of stenosis, the flow and velocity characteristics assessed by colour flow Doppler are utilized. Duplex devices also generate high resolution B-mode ultrasound images of the atherosclerotic lesion. These images do not contribute significantly to the assessment of carotid
